This invention relates to phenol and acetone production, particularly to removing salts from washed cleavage product from the reaction of cumene hydroperoxide with an acid catalyst, and to a low sodium washed cleavage product.
Sodium is a constituent of reagents commonly used in manufacturing phenol. Other metals may appear in place of or in addition to sodium. In product recovery aspects of phenol processes, metal salt constituents can hinder process efficiency and will contaminate process byproducts. Removing metals in selected aspects of the phenol process can improve process efficiencies and reduce the production of problematic byproducts.
Phenol can be produced from oxidation of cumene to cumene hydroperoxide, followed by acid catalyzed decomposition to a cleavage product comprising solutions of phenol, acetone, and byproducts that include organic acids. The decomposition is commonly called cleavage. Cleavage product is treated with alkaline wash solutions to remove acid catalyst and a portion of the organic acid byproducts. After washing, the cleavage product and wash solutions can contain salts predominantly including sodium hydroxide (NaOH), sodium bisulfate (NaHSO4), sodium sulfate (Na2SO4), sodium phenate (NaOC6H5), sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3) and sodium salts of organic acids such as formic, acetic, benzoic, propionic, and oxalic acids in various combinations. Washed cleavage product (WCP) is separated from the wash solutions and refined in recovery operations entailing distillation and separation to recover products acetone and phenol, unreacted cumene, and alpha-methylstyrene (AMS). Recovery also purges low-boiling and high-boiling byproduct impurities.
Residual salts entering the recovery operations as constituents in the washed cleavage product can result in fouling of separation and heat exchange equipment. Fouling can be delayed or slowed by operating recovery processes at reduced efficiencies. Ultimately, heavy organic waste products from the phenol process contain concentrations of salts that can present a disposal problem for the heavy organic impurities that might, for example, otherwise be burned as waste fuel.
Representative phenol manufacturing methods using various alkaline solutions to wash cleavage product are described in U.S. Pat. Nos. 2,734,085; 2,737,480; 2,744,143; 3,931,339; 4,262,150; 4,262,151; 4,626,600; 5,245,090 5,304,684; 5,510,543; 6,066,767. U.S. Pat. No. 4,568,466 to Salem et al discloses ion exchange applications to high-purity boiler feed waters. U.S. Pat. No. 4,747,954 to Vaughn et al. teaches formulations of ion exchange resins. All of these patents are hereby incorporated by reference herein in their entirety.
There is a need in the field of manufacturing phenol and acetone for improvements to benefit the efficiency and economics of production, particularly regarding productivity, recovery operations, and waste disposal. It would be desirable to improve the production of phenol and acetone in ways that (1) increase product recovery and plant availability, (2) reduce waste generation, (3) divert salt constituents out of process subsystems that incur operating and maintenance costs when elevated salt levels are characteristically present, (4) separate salt constituents from organic byproduct and waste streams to facilitate more cost effective disposal of the organics, and (5) facilitate greater internal recycle of recoverable intermediate byproducts and unused reagent, thereby reducing costs of makeup reagents.
The present invention removes cations and anions from washed cleavage product from the reaction of cumene hydroperoxide with an acid catalyst. The method contemplates using an alkaline washing operation to neutralize the acid and remove the bulk of the ions from the cleavage product. The washed cleavage product is then passed through cation and anion exchangers to remove the ions prior to distillation or other processing to recover acetone, phenol and other compounds from the cleavage product. The ion removal greatly reduces fouling in the product recovery, with less waste disposal, less operating downtime and longer operation between maintenance cycles, better heat transfer and energy efficiency, higher production rates, and the like.
In one aspect, the invention provides a process for reducing ion content of washed cleavage product from the reaction of cumene hydroperoxide with an acid catalyst. The process includes contacting the washed cleavage product with a cation exchanger to remove positively charged ions including sodium, contacting the washed cleavage product with an anion exchanger to remove negatively charged ions including sulfate, and recovering exchanger effluent lean in sodium and sulfate. The washed cleavage product supplied to the exchangers can be whole washed cleavage product, or dewatered cleavage product, e.g. obtained by coalescing the whole washed cleavage product. The washed cleavage product preferably comprises a molar ratio of acetone to phenol from 0.8 to 1.5, from 2 to 30 weight percent cumene, from 4 to 20 weight percent water, and from 10 to 400 ppmw sodium, more preferably less than 300 ppmw sodium and especially less than 200 ppmw sodium. The exchanger effluent preferably has less than 10 ppmw sodium, more preferably less than 5 ppmw, and especially less than 2 ppmw sodium.
The cation exchanger is preferably a strong acid cation exchange resin in hydrogen form, or a weak acid cation exchange resin in hydrogen form. The anion exchanger is preferably a weak base anion exchange resin in free base form, or a strong base anion exchange resin in hydroxide form. The ion exchangers can be a mixed bed of exchanger media comprising both cation and anion exchangers, preferably with an effluent having a sodium concentration less than 5 ppmw. In another embodiment, the anion and cation exchangers comprise serial beds of anion and cation exchange resins, respectively, preferably with an effluent having a sodium concentration less than 10 ppmw and a pH from 3.5 to 6.0.
The process preferably includes a cation exchange adsorption cycle at a temperature from 20xc2x0 to 80xc2x0 C. and a feed rate to the cation exchange resin bed from 1 to 60 cubic meters per cubic meter of bed volume per hour (BV/hr). A cation exchange regeneration cycle preferably employs from 0.5 to 10 weight percent aqueous sulfuric acid. The process preferably includes an anion exchange adsorption cycle at a temperature from 20xc2x0 to 80xc2x0 C. and a feed rate to the anion exchange resin bed from 1 to 60 BV/hr. An anion exchange regeneration cycle can employ aqueous NaOH, sodium phenate, or a combination thereof, at NaOH or NaOH-equivalent concentration from 0.2 to 8 weight percent.
In another embodiment, the present invention provides a process for producing phenol that includes oxidizing cumene to cumene hydroperoxide, cleaving the cumene hydroperoxide in the presence of an acid catalyst to form a cleavage product mixture including phenol and acetone, washing the cleavage product mixture with alkaline wash solution to form a washed cleavage product, contacting the washed cleavage product with a cation exchanger and an anion exchanger to form a polished cleavage product of reduced ion content, preferably as described above, and recovering phenol and acetone from the polished cleavage product. The washing can include coalescing a whole washed cleavage product to separate an aqueous phase and recover the washed cleavage product for the exchanger contacting, wherein the recovered washed cleavage product comprises a molar ratio of acetone to phenol from 0.8 to 1.5, from 2 to 30 weight percent cumene, from 4 to 20 weight percent water, and from 10 to 400 ppmw sodium, more preferably less than 300 ppmw sodium and especially less than 200 ppmw sodium.
The product recovery can include distillation of the polished cleavage product and recovery of an aqueous stream recycled to the washing step. The process can also include dephenolating spent wash water from the washing. The dephenolation can include acidifying the spent wash water and extracting phenol from the acidified wash water with an immiscible solvent obtained from the phenol and acetone recovery, and recycling the extract to the cleavage product in the washing. The process can further include regenerating the cation and anion exchanger with aqueous and organic fluids, recycling spent aqueous fluid to the dephenolation, and recycling spent organic fluid to the washing.